Heat treating apparatus for sheet or web like material



Feb. 22, 1966 H. L. SMITH, JR 3,235,973

HEAT TREATING APPARATUS FOR SHEET 0R WEB LIKE MATERIAL Filed Oct. 17,1962 2 Sheets-Sheet 1 0: 2 5 I Ll-I N (O N 8 IO N 00 a Q 4 (D N a (.0 EQ N I N g E INVENTOR Horace L Smith, J1:

ATTORNEYS Feb. 22, 1966 l H. SMITH, JR

HEAT TREATING APPARATUS FOR SHEET OR WEB LIKE MATERIAL 2 Sheets-Sheet 2Filed Oct.

R O T. m V W O M u 5 I 8 7 2 6 m 8 5 4 O 7).( mm 5 M mu 0 H 4 7 w 4 .1 94 4 4 2 O O O 2 2v 2V 0 l /4 V 51 h m 6 H R Q l l WE UT T Horace L.Smith ATTORNEYS 3,235,973 HEAT TREATING APPARATUS FOR SHEET R WEB LIKEMATERIAL Horace L. Smith, Jr., Richmond, Va., assignor to HuppCorporation, Cleveland, Ohio., a corporation of Virginia Filed Oct. 17,1962, Ser. No. 231,259 8 Claims. (Cl. 34-155) This application is acontinuation-in-part of my copending application Serial No. 166,182,entitled Heating, Drying and Curing Apparatus and Method, filed January15, 1962.

The present invention relate-s to improvements in apparatus for heattreating sheet, Web or the like material such as for example heating,drying, curing and the like. More particularly, the invention relates tonovel apparatus for processing such materials treated with or includinga substance desired to be removed from the sheet, or physically modifiedby, exposure to heat, and is therefore applicable for example in paperdrying, curing of thermoset resins, coronizing glass fabric,impregnation of materials with plastics, rubber, fixation of resinbonded dyes and pigments on web materials, single or multiple patterndyeing or otherwise treating and developing special design such as laceor open area effects, in resinous fabrics, tapes, webs, and the like.The term sheet will be hereinafter used to include sheet, web and thelike materials.

Methods and apparatus in said copending application are disclosed forovercoming disadvantages of conductive and heated air heating systemsthrough the novel use of heat transfer by radiation and simultaneouscross ventilation of the products being heated. The cross ventilationfor removing vapors as evolved during heating improves the finalproducts obtainable, and the efficiency of the system, by removing thevolatilized material from the immediate vicinity of the heaters andsheet material to avoid possible combustion, product contamination, andimpairment of evaporation or volatilization from the material undertreatment by removing the volatiles and vapors substantially as evolvedtransversely of the sheet.

I have discovered that the combination of heated air or gas streamsmoving longitudinally at relatively high velocity over the surface ofsheet while it is being heated by radiant heat produces an apparentsynergistic heating, evaporating and drying effect, i.e., in paperdrying for example, much more drying can be achieved by the combinationof radiant heat and heated air than by the sum of the effects of theindividual heating media. While substantially improved results areattained by heating the sheet from one side only in accordance with myimproved combinations, in the preferred embodiment radiant heating ofboth sides is carried out in combination with heated gas streamsconfined between the sheet material and radiators to scour the oppositesurfaces of the sheet at relatively high velocity with respect to thesheet surface movement,

nited States Patent 0 and remove the volatile substances immediatelyupon emergence in the continuously changing hot gas atmosphere, wherebyheat is simultaneously developed in the sheet, by radiant energy andcontact with heated rapidly moving air streams. The rapidly moving airstreams scour the heated volatile substances emerging, or about toemerge, as vapor, from the heated sheet. The action of the scouring gascontacting the sheet surfaces and physically aiding in removal of thevolatile substances, promotes more rapid volatilization by removing thevolatilized materials before they can condense or otherwise promote acooling or other vaporization retarding effect.

The most pertinent prior art of which I am aware is U.S. Patent2,861,354 to Hultgreen which discloses a compact device adapted tosupplement the drying capacity of Too larger apparatus. The Hultgreenapparatus is comprised of a radiator element positioned in a housingsuspended over the sheet material being dried, and a nozzle adapted toimpinge air on the sheet at an angle of between 5 and degrees withdespect to the plane of the sheet, and in a direction having a componentwhich is opposite to the direction of sheet travel. The object of theair impingement is to promote surface turbulence on the sheet surface inthe area irradiated by the radiant heater element to improve dryingefficiency. Briefly, the present invention differs from the Hultgreenapparatus in that it (a) utilizes extended area radiating units whichserve as guides for the rapidly moving air stream longitudinally of thesheet movement between direction changes, and (b) involves a completeheat treating apparatus having regulatable temperature and atmospherezones which enable multi-phase heat treatment in a single apparatus,with high efiiciency, and increased speeds. Gas streams are directedessen tially parallel to the plane of the sheet, between large panel, orbanks of, radiators to effectively impart heat to the sheet, remove thevolatilized material, and improve the over-all heating efiiciency. Inletand outlets between the legs of each run of the sheet permit regulationof the heating atmosphere in each run as desired depending on theoperating temperatunm and effect on the sheet which is contemplated fora particular run.

One particular application of my present invention is the coronizing ofglass fabric. The current glass fabric desizing, coronizing and settingprocesses, temperature ranges, and equipment and their relativeadvantages and disadvantages are disclosed in U.S. Patents to Klug2,633,528; Waggoner 2,845,364; May 2,970,934; Caroselli 3,008,846; andLotz 3,012,845. In the Klug, Waggoner and May processes, burning of theevolved combustibles occurs on the fabric with flame temperaturesconsiderably above the maximum desirable fabric setting temperatureswith adverse discoloration, considerable weakening of the fabricstrength and consequent product market value deterioration. Thesedisadvantages are to some extent avoided in the Caroselli and Lotzprocessing. In my improved apparatus, the glass fabric bearing organicsize is passed through a multiplicity of individually ventilated runs inwhich the gas being introduced, length and temperature of heaters, andspeed of travel are correlated so that flammable lower volatilematerials are removed in the initial run or runs in an inert, i.e.,non-oxidizable, atmosphere such for example as nitrogen, combustionproducts, carbon dioxide, or the like. The less combustible volatilesare removed under controlled atmospheric conditions with flamelessoxidation of the remaining volatile constituents and impurities in thefabric, thereby effecting size removal, and improving fabric strengthand colors. By operating at relatively high radiator surfacetemperatures, for example at the minimum desirable glass fabric settingtemperature, and preventing combustion of volatiles in an inertatmosphere in the low volatile removal zone, and controlled, flamelesscoronizing and setting in the processing in subsequent zones, I produceimproved, color, and strength glass fabrics with increased productionand at lower cost.

Another particularly good application of my present invention is indrying paper or other similar products. I have discovered that ahorizontal run drying apparatus embodying the principles of thisinvention may economically achieve very fast drying rates, and a productthat has been heated uniformly, or as controlled, and which hassubstantially no wrinkles, cockles, or the like physical defects presentin paper dried by conventional prior drying methods. For such use,multiple, slightly chordally arched, substantially horizontal dryingruns are prefer ably established, with radiant heaters located on bothsides of the paper sheet, and plural inlet and exhaust nozzles spacedalong the runs and adapted to pass streams of gas longitudinally of andbetween the papers and radiators. The multiple run apparatus may belocated in a conventional drying chamber, or for additionally improvedresults, in a chamber under subatmospheric pressure in which moisture inthe paper volatilizes at a lower temperature and is therefore morequickly removed, and has a reduced tendency to absorb heat radiation.

It is therefore a .primary object of this invention to provide novelradiant heating apparatus for drying, and/ or curing sheet materialsimpregnated or coated with volatile or heat transformable substances byutilization of radiant heaters in controlled atmospheres.

Another object is to provide novel apparatus in which sheet heattreating, particularly desizing and coronizing glass fabric, and dryingpaper and the like materials, may be carried out in one or more heatingzones defined by radiant heater elements, and in which the heatingeffect of the radiators is supplemented by a gaseous stream or' streamspassing in contact with the heated surfaces of the sheet material atrelatively high velocities.

I Another object is to provide a novel apparatus including radiantheater elements defining a heating zone,

guide means for passing the sheet through the heating zone andventilating means for passing a stream or streams of gas longitudinallyover the surfaces of the sheet material at relatively high velocitieswith respect to the speed' of sheet movement.

A further object is to provide, if desired, one or more improved paddersor other suitable devices, for treating the material at variousintervals in the heat treating process.

Still another object is to provide novel apparatus for heat treatingsheet material in a plurality of substantially horizontal or verticalruns each comprised of a pair of draw sections between spaced rollers,in which a stream of air or other gas is passed over at least one sideof the sheet in the draw sections while being exposed to heat radiationfrom heater elements.

Still other objects of this invention are to provide a novel heatingelement with heat exchange fins thereon adapted to coact with gasstreams being passed over the product to provide for improved control ofgas flow over the sheet surfaces, and to provide improved apparatus fordirecting streams of gas along the surface of the material beingtreated, including gas supply and exhaust plenums with nozzles fordirecting the gas longitudinally of the material surfaces in runsbetween rollers in which the gas is deflected by rollers opposite thesupply plenums and in which the exhaust receives the deflected streamsof gas at the end of oppositely traveling sheet draw.

Other objects and advantages of the present invention will becomeapparent from the appended claims and following description 'of the bestmode of carrying out the present invention and modifications thereof,and from the accompanying drawing wherein:

FIGURE 1 is a sectional side elevation taken along line 1-1 of FIGURE 3,of a multiple run diagrammatically illustrated apparatus embodying theprinciples of the present invention;

FIGURE 2 is an end elevation of the apparatus illustrated in FIGURE 1with portions of the casing of the apparatus broken away to illustrateits internal structure;

FIGURE 3 is a plan view of the apparatus illustrated in FIGURE 1 andshowing the section line 11 along which FIGURE 1 was taken;

FIGURE 4 illustrates a modified multiple run arrangement and gas plenumslocated adjacent each roller in the run in the apparatus; and

FIGURE 5 illustrates an improved radiating element for providing radiantenergy to the sheet being heat treated.

Referring now to the drawings, in FIGURE 1 product 10 is shown passinginto a multiple run heat treating app t s located in housing 14, and wich is preferably utilized in desizing glass fabric. Sheet 10 may beguided into and through the apparatus in any suitable manner, as forexample, by guide roller 18 and rollers 20, 21, 22, 23, 24, 25, 26, 27,and 28. The number of rollers will depend on the number of runs in theapparatus. The rollers may be idler or driven. If driven, a common motorwith belt hook-up for example may be used, or individual roller powerunits may be used if it is desired to operate the rollers individuallyat differing speeds, for example, to compensate for expansion andcontraction under differing temperature conditions of the individual.Radiators 32, preferably double faced with separately regulatablesurface temperatures, extend from the bottom of the apparatus up to apoint near rollers 21, 23, 25, and 27 and double face radiators 36extend from the top downwardly to a point near rollers 22, 24, 26, and28 Alternately supporting the radiators from opposite ends creates, ineffect, a plurality of partitions between each radiator pair in whichindividual heating zones are established and operating temperatures maybe controlled substantially as desired depending on location of theparticular zone and the sheet treatment :phase. The over-all arrangementof the radiators 32 and 36 is such that substantially continuouscontrolled heat treatment of the material is effected as it passesthrough the apparatus.

As shown in FIGURE 1, gas is circulated over the upper and lowersurfaces of sheet 10 while it is being irradiated, by a dividedventilating system comprised of upper and lower ventilating unitsindicated generally a and 51 respectively. Gas circulated by upperventilating unit 50 is indicated by dash and dot arrows and solid linearrows indicate gas being circulated by lower unit 51. Upper ventilatingunit 50 is comprised of a manifold inlet duct 54 and connecting gasinlet plenums 58, 62 and 66, a manifold outlet duct and connectingoutlet plenums 74-, 76 and 78. A blower 82 (FIGURES 2 and 3) powered bymotor 83, draws in gas from a suitable source, the atmosphere forexample, or a source of inert gas such as nitrogen or products ofcombustion from high temperature gas fired radiators for example,employed in a high temperature heating zone. The gas is then circulatedthrough an air damper 86, and heater is heated gas is desired and notalready heated as in the case of the products of combustion for example,and into inlet duct 54 and through the restricted blower outlet nozzlesof plenums 58, 62 and 66. The gas travels downwardly over the surface ofan upwardly directed leg around the bottom edge of heaters 36 and isexhausted from the heating zone through the outlet plenums 74, 76, and78 (FIG- URES 1 and 3). Gas collected in main outlet duct 70 isrecirculated to blower 82 and if desired, passed again into the heatingzone. If the gases are vapor laden with volatiles evolved during theheating process in the heating zone, they may be entirely or partiallyexhausted through an exhaust outlet provided with a damper 94 (FIGURE 3)if desired, or passed in heat exchange relationship around blower 82 ora portion of inlet duct 54 to utilize the heat carried thereby, butwithout contaminating new gas being forced into the heating zone. Thearrangement for lower ventilating system 51 (FIGURES 1, 2, and 3) isessentially the same as that of upper system 50. A blower powered bymotor? 102 is provided to supply gas. A manifold inlet duct 106 enteringat the bottom of housing 14 is provided! With a control damper 110 and aheater 114 also pro-- vided with a suitable bypass duct (not shown) ifheating; is not desired.

Gas forced through inlet duct 106 is introduced into the heating zone incontact with the under surface off sheet 10 through inlet plenums 118,122, 126, and 130,, passes upwardly along the upward leg of each sheetrun, over the top edge of radiator elements 32 at which: point it isdeflected down into exhaust plenums 134, 136, 138, and where it isintroduced into manifold outlet duct 144 for recirculation throughblower 100, partial or complete exhaustion through exhaust damper 150,or to a portion of duct 106 in heat exchange relation therewith to heatincoming gas.

It is possible to arrange the ducts in either the upper or lower gasventilating systems so that the gases in contact with both sheet or websurfaces will travel in the direction of travel of the sheet. However,it has been found preferable to circulate them countercurrently asillustrated by the arrows in the drawings.

In desizing glass fabric, at high speeds, in accordance with thisinvention, the first zone is preferably operated above the combustiontemperature of the most flammable size constituents and no higher thanthe fabric setting temperature (between about l100 and 1250 F.) in anatmosphere incapable of supporting combustion and at a speed sufficientto expose the fabric to the high temperature for only enough time toheat and volatilize or sublimate the combustible size constituents.Final coronizing and setting may then, if desirable, be effected in afinal flameless controlled oxidizing atmosphere. This permits exposureof the fabric to very high temperature and consequent fast removal ofthe more volatile, combustible constituents of the size material, yetprevents damage to the fabric as experienced in prior methods in whichthe size has been burned ofi? resulting in adverse discoloration andweakening of the fabric.

In the first run (a run as used herein, refers to two adjacent legs offabric contacting three consecutive rollers as shown in the drawing)radiator temperatures of about 500 F. to 1500 F. are preferred toquickly vaporize the lower temperature volatiles and most readilycombustible constituents that may be embodied in the material undertreatment. It is preferable to circulate sufiicient non-oxidizingnitrogen, carbon dioxide or gas radiator combustion products throughabout both sides of the fabric constituting the first run, i.e., thefirst up and down legs to prevent combustion of the volatilized orsublimated constitutents. In addition to maintaining the atmosphere ofthe initial high temperature zone incapable of supporting combustion,the run is timed through the hot zone in a manner to prevent injury tothe web. So long as liquid sublimable volatile constituents are beingvaporized the temperature of the material cannot rise above thevaporizing, boiling or sublimation temperatures of constituents to beremoved. After removal of the lower vaporizing point, more combustiblevolatiles, the speed of material may be reduced through successiveradiant heating zones to speed the removal of higher boiling, higherignition point, volatiles and sublimates without raising the temperatureof the web, sheet or fabric under treatment sufficiently high to damageit, by control of the atmosphere of the heating zones depending upon thecharacter of the material under treatment, the economics of theoperation and the desirability\ of maintaining neutral, oxidizing orreducing atmospheres, or utilization or elimination of convection in theheating and curing processes. Where the higher temperatures are used,for example, in removing yarn size material from glass fabric, radiantburners heating only one side of the material may be used since thetemperature drop across the material will be relatively slight, thuseffecting large savings on fuel and equipment heretofore used in suchoperations. However, as shown in FIGURES 1 and 4, double face radiatorsare preferred for greatest speed.

The spacing of the control switch mechanisms below the driving rollersmay be uniform or varied to provide equal or differing festoon lengthsto provide equal or differing relative times of passage of the materialthrough the successive radiation zones depending upon the material to betreated. In the subsequent runs it may be desirable to operate at veryhigh temperatures since after the initial run or runs, only hightemperature volatiles will remain on the fabric, and to keep pace withthe rapid movement of the fabric through the first runs, filamenttemperatures 6 up to 4000 F. may be desired. In the preferred operationof this invention, after fabric temperatures of 400- 1300 F. have beenachieved, subsequent radiator temperatures should be in the order of12002200 F. until the size is removed and in this last heating fiamelessoxidation of the remaining constituents is permitted to occur for mostrapid results as discussed in my copending application Serial No.166,182.

The types of radiators in each section may be selected in accordancewith the zonal temperatures and other conditions desired as thetreatment of the material proceeds. For certain types of operation,radiator temperatures up to about 800 F. are required. For these, myimproved radiators, utilizing high temperature heat transfer highboiling point hydrocarbon liquid media may be used (suitable media ofthis type are identified in copending parent application No. 166,182).For higher zonal temperature operation well known types of gas burningradiators may be used such as flame heated imperforate metal panel typeradiators. F or still higher zonal temperatures radiating surfacesoperating up to 1500 F. or higher, gas burning perforated ceramic tileoperating between about 1200-2200 F. (as for example the well knownpanel or muflie type radiators, or Perfection-Schwank type perforatedceramic tile gas burning radiators described in United States Patent No.2,775,294 and the like) may be used. The Perfection-Schwank type burnersfunction entirely on controlled gas and primary air with complete fuelcombustion and evolution of fully oxidized combustion products which aredischarged from the radiating surfaces and are incapable of supportingcombustion of the evolved volatiles. These hot gases emit radiant energyand may also be used for added convection heating of products which arenot sensitive to the evolved gases. For still higher temperatureoperation electrically heated radiators such as resistance bar andfilament heated bulb and quartz tube radiators that operate up to 4000F. and higher may be used.

In subsequent runs the less combustible, less volatile constituents andimpurities on the glass fabric are removed at higher temperaturesdeveloped by longer run lengths, higher radiator temperatures, or acombination thereof. Controlled introduction of an atmosphere containingcontrolled amounts of oxygen in combination with the high temperatureradiators effects a fiameless oxidation to the remaining volatileconstituents and impurities as discussed in my copending applicationSerial No. 166,182.

Another duct arrangement for ventilating the heating zone is illustratedin FIGURE 4, wherein alternate plenums in both upper and lower systemsare adapted to be inlet and exhaust. Thus, plenums and 174 in the uppersystem are exit plenums while 178 is an inlet plenum as indicated by thearrows in FIGURE 4, fluid flowing from plenum 173 into the heating zone,passing around the lower end of radiators 36, and upwardly into theadjacent plenums 170 and 174 and to exhaust. Similarly, in the lowersystem, 180 and 184 are exhaust plenums while plenum 188 introduces gasinto the heating zone.

The various plenums illustrated in FIGURE 4 are sub stantiallyidentical, and each has a hollow, boxlike configuration and a circularlysectioned top 190 which is concentric with and juxtaposed to theassociated web supporting roller 192. Ingress to and egress from theplenums is afforded by a slot 194 in each cover 190 which preferablyextends the length of the associated roller to insure a uniform flowpattern across the width of the Web. Sealing members 196, fixed betweenadjacent plenums in the embodiment of FIGURE 4, prevent fluid fromescaping from the heating apparatus between the plenums.

FIGURE 5 illustrates in more detail an improved radiating element whichmay be utilized in the present invention. The radiating panelsthemselves are preferably constructed in accordance with the preferredradiating elements described in detail in my copending applicationSerial No. 166,182 in that they are panels comprised of tubular channels200 through which heating fluid is circulated and heats both sides ofthe tubes, the connecting webs 202 and fins 204 to radiatingtemperatures. Fins 204 located between each of the hot fluid circulatingchannels 200 to prevent the gases passing through the heating zone fromcontacting the surfaces of the channels 200 and possibly cooling themslightly and to aid heat transfer to the sheet, and also to insure thatthe gases passing through the heating zone will remain substantially incontact with the surfaces of sheet 14 Webs 202, provide emittingsurfaces between tubes 200 so that the area of emitting surface of eachpanel is substantially equal to its total area.

Instead of vertical runs, the sheet may be passed horizontally betweenradiators with suitable modification of the ventilating apparatus todirect gas streams across the horizontal legs of the sheet. This isparticularly helpful in paper driving since the vertical run arrangementwill create high tensile stresses in the paper, requiring shorter runsto prevent breakage.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. Multiple run heating apparatus for webs of sheet material,comprising:

(a) web guiding rollers disposed in spaced apart rows and arranged toform a web of sheet material trained alternately over successive rollersin opposite ones of said rows into a plurality of generally parallelruns;

(b) a series of parallel, spaced apart radiant heaters between said rowsof rollers for evolving at least one volatile substance from said webwithout imparting significant heat to the atmosphere between saidheaters and said web, said heaters being panels comprised of tubularchannels having therein a liquid heat transfer media with a boilingpoint in the range of from about 500 to about 800 F., said heaters beingso located that the runs of said web pass therebetween;

(c) fluid circulating means for effecting a flow of fluid between theruns of the web and the rad1ant heaters and generally parallel to saidweb to remove from adjacent said web the substances evolved therefrom bysaid radiant heaters including supply and exhaust duct means;

(d) means establishing fluid communication between said supply andexhaust duct means, whereby said fluid may be recirculated through saidheating apparatus;

(e) means for controlling the proportion of evolved substances in therecirculated fluid including means for discharging a selectivelyvariable proportion of the fluid flowing in said exhaust duct meanstherefrom and means for admitting fluid which is relatively free fromsaid substances at a selectively variable rate to said supply ductmeans; and

(f) means independent of the operation of said radiant heaters forcontrolling the temperature of said fluid including at least one heatingunit for raising the temperature of the fluid as it flows through saidduct means, said heating unit supplying the major portion of the heatadded to said fluid.

2. Multiple run heat treating apparatus as defined m claim 1, whereinsaid fluid circulating means further includes supply and exhaust plenumsbetween said rollers with each supply plenum opposite an exhaust plenum,associated supply and exhaust plenums being in opposite ones of saidrows and said supply plenums communicating with said supply duct meansand having nozzles spanning the length of said rollers for dischargingstreams of fluid between said radiant heaters and the runs of said web.

3. Heat treating apparatus as defined in claim 2, where in:

(a) each of said nozzles terminates in a discharge opening locatedbetween a plane including the centerlines of the rollers in the row inwhich said nozzle is located and a plane tangent to the aforesaidrollers and on the side of said row nearest the other row of rollers;and

(b) the exhaust plenums have inlets thereto, said exhaust plenums andinlets being similar in configuration to the supply plenums and nozzlesthereof and disposed in mirror image relation thereto.

4. Multiple run heat treating apparatus as defined in claim 2, whereinsaid supply and exhaust plenums comprise:

(a) a hollow boxlike structure extending beyond the side of theassociated roller remote from the opposite row of rollers and partiallysurrounding said roller;

(b) a cover for each said plenum concentric with and juxtaposed to theassociated roller;

(0) a slit in each cover extending the length of the roller associatedtherewith; and

(d) sealing means extending between adjacent plenums to prevent fluidfrom escaping from the heat treating apparatus between said plenums.

5. Heat treating apparatus for webs of sheet material,

comprising:

(a) sheet guiding rollers in parallel, spaced, side-byside relationshipin two parallel spaced apart rows with the rollers in one row oppositethe spaces in the opposite row and the distance between rollerssubstantially equal to the diameter of the rollers, whereby a web ofsheet material trained alternately over successive rollers in oppositerows will extend between said rows in a plurality of parallel spacedapart runs;

(b) a radiant heater parallel to and between each pair of adjacent runsand adapted to heat a web of sheet material moving through the heatingapparatus in said runs, said heaters being rectangular flat panels andhaving a width at least equal to the length of the rollers and beingcomprised of tubular channels having therein a liquid heat transfermedia with a boiling point in the range of from about 500 to about 800F., one end of each heater being opposite and spaced from a roller inone of said roller rows and the opposite end of each said heater beingbetween adjacent rollers in the other of said rows and beyond a planetangent to the sides of said adjacent rollers, whereby each of saidheaters, the web moving along runs between which it is disposed, and theroller opposite the heaters one end constitute a generally U-shapedpassage having juxtaposed first and second ends between said adjacentrollers, adjacent heaters being opposite and spaced from rollers inopposite rows, whereby the openings of adjacent passage are betweenrollers in the opposite ones of said rows;

(c) means for scouring evolved vapors from adjacent the surfaces of theweb facing each heater in the two runs associated therewith comprisingmeans for forcing a stream of fluid through each of said U- shapedpassages and generally parallel to the runs of said web including asupply plenum adjacent and in fluid communication with one end of eachpassage and an exhaust plenum adjacent and in fluid communication withthe other end of each of said passages and supply and exhaust duct meanscommunicating with said supply and exhaust plenums, respectively;

(d) means establishing fluid communication between said supply andexhaust duct means, whereby said fluid may be recirculated through saidheating apparatus;

(e) means for controlling the proportion of evolved substances in therecirculated fluid including means for discharging a selectivelyvariable proportion of the fluid flowing in said exhaust duct meanstherefrom and means for admitting fluid which is relatively free fromsaid substances at a selectively variable rate to said supply ductmeans; and

(f) means independent of said radiant heaters for controlling thetemperature of said fluid including at least one heating unit forraising the temperature of the fluid as it flows through said ductmeans, said heating unit supplying the major portion of the heat addedto said fluid.

6. Heat treating apparatus as defined in claim 5,

wherein:

(a) said supply plenums are at least as long as said rollers and includeinlet nozzles in fluid communication with the interiors of said plenumsand extending substantially the length thereof;

(b) said exhaust plenums are at least as long as said rollers andinclude exhaust inlets in fluid communication with the interiors of saidexhaust plenums and extending substantially the length thereof; and

(c) the supply and exhaust plenums associated with each of said fluidpassages are disposed in parallel spaced relationship with the dischargeopening of the supply plenum nozzle midway between one side of theassociated heater and the run thereadjacent and the inlet to the exhaustplenum midway between the other side of said heater and the runthereadjacent.

7. Multiple run heat treating apparatus as defined in claim 1, wherein:

(a) the tubular channels of said radiant heaters are arranged inparallel, side-by-side relationship to form planar arrays; and

(b) said heaters further include webs between adjacent tubular channelsto provide emitting surfaces therebetween and fins extendingsubstantially normal to said webs to reduce the transfer of heat fromsaid webs to said fluid by minimizing the contact of said fluid withsaid webs and said tubular channels.

8. Heat treating apparatus for webs of sheet material,

comprising:

(a) sheet guiding rollers in parallel, spaced, side-byside relationshipin two parallel spaced apart rows;

(b) a supply plenum and an exhaust plenum between each pair of adjacentrollers in each of said rows,

said supply and exhaust plenums being at least equal in length to saidrollers;

(c) the supply plenums associated with each row all having inletsthereto at one side of the rollers in said row and the exhaust plenumsassociated with the same row all having outlets on the opposite side ofthe rollers in said row;

(d) there being associated with each of said rows an independent fluidcirculation system for eifecting a flow of fluid adjacent and generallyparallel to the runs of a web of sheet material trained alternately oversuccessive rollers in the opposite ones of said rows to thereby scourfrom adjacent the web volatile substances evolved therefrom, each saidsystem comprising a blower, supply duct means connected between saidblower and the inlets to the supply plenums in the associated row, andexhaust duct means connected between said blower and the outlets fromthe exhaust plenums in said row;

(e) a plurality of radiant heaters in the space between said rows ofrollers for heating a web of sheet material moving through saidapparatus;

(f) means establishing fluid communication between said supply andexhaust duct means, whereby said fluid may be recirculated through saidheating apparatus;

(g) means for controlling the proportion of evolved substances in therecirculated fluid including means for discharging a selectivelyvariable proportion of the fluid flowing in said exhaust duct meanstherefrom and means for admitting fluid which is relatively free fromsaid substances at a selectively variable rate to said supply ductmeans; and

(h) means independent of said radiant heaters for controlling thetemperature of said fluid including at least one heating unit in each ofsaid supply duct means for raising the temperature of the fluid as itflows through said duct means, said heating units supplying the majorportion of the heat added to said fluid.

References Cited by the Examiner UNITED STATES PATENTS 2,101,301 12/1937Wellmar 34-157 X 2,268,986 1/1942 Hess 34-46 X 2,269,236 1/1942 Wellmar34-161 X 2,553,516 5/1951 French 34-36 X 2,807,097 9/1957 Kullgren eta1. 34-68 3,151,950 10/1964 Neuman et al. 34-41 X FOREIGN PATENTS580,646 7/1933 Germany.

16,799 5/ 1898 Switzerland.

WILLIAM F. ODEA, Primary Examiner.

NORMAN YUDKOFF, Examiner.

1. MULTIPLE RUN HEATING APPARATUS FOR WEBS OF SHEET MATERIAL,COMPRISING: (A) WEB GUIDING ROLLERS DISPOSED IN SPACED APART ROWS ANDARRANGED TO FORM A WEB OF SHEET MATERIAL TRAINED ALTERNATELY OVERSUCCESSIVE ROLLERS IN OPPOSITE ONES OF SAID ROWS INTO A PLURALITY OFGENERALLY PARALLEL RUNS; (B) A SERIES OF PARALLEL, SPACED APART RADIANTHEATERS BETWEEN SAID ROWS OF ROLLERS FOR EVOLVING AT LEAST ONE VOLATILESUBSTANCE FROM SAID WEB WITHOUT IMPARTING SIGNIFICANT HEAT TO THEATMOSPHERE BETWEEN SAID HEATERS AND SAID WEB, SAID HEATERS BEING PANELSCOMPRISED OF TUBULAR CHANNELS HAVING THEREIN A LIQUID HEAT TRANSFERMEDIA WITH A BOILING POINT IN THE RANGE OF FROM ABOUT 500 TO ABOUT800*F., SAID HEATERS BEING SO LOCATED THAT THE RUNS OF SAID WEB PASSTHEREBETWEEN; (C) FLUID CIRCULATING MEANS FOR EFFECTING A FLOW OF FLUIDBETWEEN THE RUNS OF THE WEB AND THE RADIANT HEATERS AND GENERALLYPARALLEL TO SAID WEB TO REMOVE FROM ADJACENT SAID WEB THE SUBSTANCESEVOLVED THEREFROM BY SAID RADIANT HEATERS INCLUDING SUPPLY AND EXHAUSTDUCT MEANS; (D) MEANS ESTABLISHING FLUID COMMUNICATION BETWEEN SAIDSUPPLY AND EXHAUST DUCT MEANS, WHEREBY SAID FLUID MAY BE RECIRCULATEDTHROUGH SAID HEATING APPARATUS; (E) MEANS FOR CONTROLLING THE PROPORTIONOF EVOLVED SUBSTANCES IN THE RECIRCULATED FLUID INCLUDING MEANS FORDISCHARGING A SELECTIVELY VARIABLE PROPORTION OF THE FLUID FLOWING INSAID EXHAUST DUCT MEANS THEREFROM AND MEANS FOR ADMITTING FLUID WHICH ISRELATIVELY FREE FROM SAID SUBSTANCES AT A SELECTIVELY VARIABLE RATE TOSAID SUPPLY DUCT MEANS; AND (F) MEANS INDEPENDENT OF THE OPERATION OFSAID RADIANT HEATERS FOR CONTROLLING THE TEMPERATURE OF SAID FLUIDINCLUDING AT LEAST ONE HEATING UNIT FOR RAISING THE TEMPERATURE OF THEFLUID AS IT FLOWS THROUGH SAID DUCT MEANS, SAID HEATING UNIT SUPPLYINGTHE MAJOR PORTION OF THE HEAT ADDED TO SAID FLUID.